The invention relates to a system for controlling an automatically shifting transmission having a first selecting device for fixing adjustable drive positions in an automatic mode, and a second selective device for triggering direct upshifting and/or downshifting.
Such a system is known, for example, from German Patent Document DE 197 36 406 A1. This system has a first selecting device in the form of a selector lever by which the drive positions P, R, N, D can be fixed, and which can be adjusted in an automatic mode. Using a second selecting device in the form of a steering wheel having two switches, the gears of the transmission can be manually shifted up or down in steps in a manual mode. The known system has an electronic transmission control device which is customary in the case of automatic transmissions or automated manual transmissions. According to the system known from German Patent Document DE 197 36 406 A1, that the manual mode is activated with the operation of the second selecting device starting from the automatic mode. This manual mode is maintained until situations are detected in which the automatic mode is desirable.
During a transition from the manual mode to the automatic mode, gear change operations may be carried out by the known system that are not expected by the driver. On the one hand, a transition to the automatic mode after the manual mode had been maintained for a fairly long time cannot be comprehended or expected by the driver. On the other hand, the software modules in the control device which are assigned to the two modes are not mutually coordinated, so that uncomfortable gear change operations may occur. Maintaining the manual mode for a given time is particularly disadvantageous because, after the expiration of the given time, certain shifting operations, which are not yet concluded, possibly have to be interrupted. Furthermore, a change from an automatic mode to the manual mode and back involves further interface functionalities or special complementary functions, such as the gear display or the further development of automatic upshifts/downshifts at rotational speed limits, and others.
The embodiments of the invention provide a comfort-optimized shifting strategy for automatic or automated transmissions, which may be achieved by starting in the automatic mode when the second selecting device are provided, and although a direct upshifting or downshifting is permitted, the automatic mode is maintained such that a gear change following this upshifting or downshifting is carried out corresponding to the shifting logic of the automatic mode. Advantageous further developments are described further below.
By using the system according to the invention, particularly by using a corresponding programming of the electronic control device when operating the second selecting device starting from the automatic mode, a direct upshifting or downshifting is permitted, in which case, however, no transition takes place into the manual mode.
A gear change following this upshifting or downshifting is carried out corresponding to the shifting logic of the automatic mode. In the case of a multiple operation of the second selecting device, multiple direct upshifts and downshifts respectively may also be permitted but always without leaving the automatic mode. The reason is that only the shifting logic on which the automatic mode is based also monitors operating parameters which have to be taken into account particularly with respect to comfort during gear shift operations. The second selecting device may also be a sports key or another key by which, corresponding to at least its functional configuration, an upshifting or downshifting is triggered arbitrarily.
Preferably, it is provided that, starting from the automatic mode before the operation of the second selecting device, another operating element has to be actuated in order to shift over into the manual mode. However, if the second selecting device is operated without any previous operation of the other operating element, the above-mentioned function is initiated.
Preferably, the duration of the operation of the second selecting device can be detected and the gear engagement on the basis of the directly permitted upshifting or downshifting can be maintained at least for the duration of the operation of the second selecting device. According to this further development of the invention, the driver can deliberately determine the minimum duration of maintaining this gear.
In a further embodiment of the invention, the shifting logic of the automatic mode contains a gear change prevention which, after the implementation of a gear change, or in this exemplary case after the implementation of the upshifting or downshifting triggered by the second selecting device, until a defined event is present, prevents another gear change when the latter is predefined according to the characteristic shifting curves present in the shifting logic. As a result, pendulum shifting is prevented.
A defined event is, for example, first a change of a power demand signal and/or of the vehicle velocity after an upshifting or downshifting carried out by operating the second selecting device.
The defined event is or preferably includes also the falling below a predefined threshold value with respect to the change of the power demand signal and/or of the vehicle velocity.
This preferably requires that, after the upshifting or downshifting carried out by the operation of the second selection device, a waiting first takes place for a change of the power demand signal and/or of the vehicle velocity. The reason is that otherwise the gear change prevention would not be effective if the power demand signal and the vehicle velocity were to remain constant, which could result in an undesirable pendulum shifting. A defined event is therefore preferably first the waiting for a change of the power demand signal and/or of the vehicle velocity and the subsequent falling below a predefined threshold value with respect to the change of the power demand signal and/or of the vehicle velocity.
In this exemplary embodiment, only the amount of the change, not the direction of the change plays a role. A power demand signal may, for example, be a request of a driver assistance system for tractive power or an accelerator pedal angle or a signal proportional to the braking pressure from which, in each case, the positive or negative tractive force wish of the driver can be determined. This further development is mainly relevant in connection with the driver's acceleration wish, after which normally a leveling-out to a new steady-state operating point takes place. For this purpose, the driver normally desires a downshift and simultaneously depresses the accelerator pedal. Thus, as long as the accelerator pedal angle changes in a predefined tolerance band and a steady-state operating point is therefore not reached, a gear shift is prevented according to the invention. Here also, the avoidance of undesired pendulum shifts is in the foreground.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.